FLUTTER
09-16-2007 | 04:09 PM
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From: Burley,
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FLUTTER
Was at the field this weekend watching my buddy fly his Funtana 90 with a Saito 1.8 in it. Well the short of it, he came pretty hot on a down line and one of the ailerons ftarted to flutter. Right wing departed the plane and it piled up in a potatoe field. Upon examination of the wreckage the left aileron servo stripped all the gears. These were good JR digitals.
Flutter will destroy an airframe so fast. I noticed a few things. As this was an arf it was assembled with the supplied hardware. Personally on that size of a plane with that large an engine and doing 3d stuff I would have upgraded the control horns and linkages. I do not know if the control horn on the right aileron broke from stress, flutter, or the crash but I would not trust those white control horns to that kind of stress. They would probabally work well on a large cub or an easy flier but to take the stress of an aileron that is 1/3 the cord of the wing or a rudder that is 1/2 the surface orea of the vertical stab just isn't worth it to me.
Better hardware and tight strong links to the servos on a plane like that is critical.
Flutter will destroy an airframe so fast. I noticed a few things. As this was an arf it was assembled with the supplied hardware. Personally on that size of a plane with that large an engine and doing 3d stuff I would have upgraded the control horns and linkages. I do not know if the control horn on the right aileron broke from stress, flutter, or the crash but I would not trust those white control horns to that kind of stress. They would probabally work well on a large cub or an easy flier but to take the stress of an aileron that is 1/3 the cord of the wing or a rudder that is 1/2 the surface orea of the vertical stab just isn't worth it to me.
Better hardware and tight strong links to the servos on a plane like that is critical.
09-16-2007 | 08:23 PM
#5
My Feedback: (28)
RE: FLUTTER
There's nothing wrong with twice the size engine. I fly the Hangar 9 Mustang (60) with the pumped OS 120. You can never have enough power until it starts messing with your wing loading as far as I'm concerned. (i.e. putting a 200 on a 40 size).......I think my next Mustang (60) as a sister plane to my current one will be highly modified before construction begins and include a YS 160 DZ for power to be the scale equivalent to this...............
09-16-2007 | 08:39 PM
#7
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RE: FLUTTER
A YS 160 DZ will be a little more than the same thing. I'll probably be pushing the limit of 60 Mustang with that. Got to love carbon fiber. The one I have now only clocked 120 today on the radar gun. I'm looking for the scale speed for the next one. Strega runs in the oh....480mph range
09-17-2007 | 01:22 PM
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From: Jacksonville, FL
RE: FLUTTER
you can reduce the chance for flutter by sealing the gaps in the hinge lines...if your using pined hinges counter sink the part of the hinge where the pin is to help reduce the gap. but by all means seal the gap..will help the control surfaces have better authority too.
09-17-2007 | 03:10 PM
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From: whitehaven, UNITED KINGDOM
RE: FLUTTER
Hi, i agree on the sealing gaps up
but ... that model flies at my site with a reccommended os 91fx .. it will fly imac full 3d and every thing in the book using the throttle any where from idle to full ... The engine size in the model was the problem because of the size of the control surfaces on it... if the model were the likes of a mustang or even somthing like a 90 size extra.. the story would be different because the controll surfaces wouldn't be prone to flutter at such high speeds (created by the larger engine thrust) unlike those on a funfly .....
Just my chips
Henley
but ... that model flies at my site with a reccommended os 91fx .. it will fly imac full 3d and every thing in the book using the throttle any where from idle to full ... The engine size in the model was the problem because of the size of the control surfaces on it... if the model were the likes of a mustang or even somthing like a 90 size extra.. the story would be different because the controll surfaces wouldn't be prone to flutter at such high speeds (created by the larger engine thrust) unlike those on a funfly .....
Just my chips
Henley
09-17-2007 | 07:14 PM
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From: Burley,
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RE: FLUTTER
The engine was not a factor in this case. He was at idle on a down leg and the flutter started. I feel that not sealing the gaps combined with the cheaper hardware and the speed came to make a bad combination.
A little slop in the system and the cheap plastic horns on large control surfaces, not a good combination.
A little slop in the system and the cheap plastic horns on large control surfaces, not a good combination.
09-17-2007 | 11:02 PM
#13
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RE: FLUTTER
....the flutter on this type of plane comes from the huge control surfaces, and high speed.
These surfaces are not sealed on the seams, which doesn't really matter....nor are they
strong enough to resist flexing at speed....which results in flutter....and they usually extend
out to the wingtips, which invites flutter.
The bottom line is....don't fly most 3-D planes too fast....'yer asking for flutter.
FBD.
These surfaces are not sealed on the seams, which doesn't really matter....nor are they
strong enough to resist flexing at speed....which results in flutter....and they usually extend
out to the wingtips, which invites flutter.
The bottom line is....don't fly most 3-D planes too fast....'yer asking for flutter.
FBD.
09-18-2007 | 05:32 AM
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From: Jacksonville, FL
RE: FLUTTER
flutter is caused by airflow between the wing and control surfaces which causes the control surface to deflect. which causes the airflow to reverse and the control surface to deflect the other way, which causes the airflow to reverse etc etc until it breaks....makes an unforgettable buzzing sound. Will happen at high speeds..
since we'll never get the NTSB report on this one ryanpilot could be correct...
flutter at high speed is caused by..too big a gap between the control surface and wing...weak servo, control horn, clevis, or control rod that will flex. even broken or loose hinges. Did the engine size contribute to the accident perhaps. might have over stressed some of the control surface componets on a previous manuver. Sealing the gap would have prevented flutter.
flutter also can effect our full scale cousins..but that issue is layed to rest in the testing stages.or now a days on the computer.before production begins.
Now before you get worried flutter won't have an effect on trainers. Should have seen the gap I had on my LT-40. a hignge pin widith worth...
Sorry for the loss of the plane
since we'll never get the NTSB report on this one ryanpilot could be correct...
flutter at high speed is caused by..too big a gap between the control surface and wing...weak servo, control horn, clevis, or control rod that will flex. even broken or loose hinges. Did the engine size contribute to the accident perhaps. might have over stressed some of the control surface componets on a previous manuver. Sealing the gap would have prevented flutter.
flutter also can effect our full scale cousins..but that issue is layed to rest in the testing stages.or now a days on the computer.before production begins.
Now before you get worried flutter won't have an effect on trainers. Should have seen the gap I had on my LT-40. a hignge pin widith worth...
Sorry for the loss of the plane
09-18-2007 | 02:23 PM
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From: Jacksonville, FL
RE: FLUTTER
well NFO you'd be correct if the thrust to weight ratio was the same...however it isn't the RC airplane has a lot more thrust to weight than its full scale counter part...a 60 size Stang will do better than 68 MPH...A SIG LT-40 with a .46 will do 70 flat out.
09-18-2007 | 03:40 PM
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From: Auburn,
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RE: FLUTTER
ORIGINAL: jetmech05
well NFO you'd be correct if the thrust to weight ratio was the same...however it isn't the RC airplane has a lot more thrust to weight than its full scale counter part...a 60 size Stang will do better than 68 MPH...A SIG LT-40 with a .46 will do 70 flat out.
well NFO you'd be correct if the thrust to weight ratio was the same...however it isn't the RC airplane has a lot more thrust to weight than its full scale counter part...a 60 size Stang will do better than 68 MPH...A SIG LT-40 with a .46 will do 70 flat out.
The one I have now only clocked 120 today on the radar gun. I'm looking for the scale speed for the next one. Strega runs in the oh....480mph range
Phil
09-20-2007 | 10:17 AM
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From: Guymon,
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RE: FLUTTER
Throttle boys, throttle, don't need full throttle to fly, throttle management, can't have to much power, left stick back for less throttle, it works trust me!!!!!!!!!
enough said!!!
enough said!!!
09-20-2007 | 05:45 PM
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From: Yokosuka, Japan
RE: FLUTTER
I have to continualy remind myself when I fly on windy days that the reason the plane is having problems is that a 15 mile an hour wind is a 105 mile an hour scale wind for 1/7 planes, just food for thought
09-21-2007 | 08:47 AM
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From: Cape TownWestern Cape, SOUTH AFRICA
RE: FLUTTER
ORIGINAL: jetmech05
flutter is caused by airflow between the wing and control surfaces which causes the control surface to deflect. which causes the airflow to reverse and the control surface to deflect the other way, which causes the airflow to reverse etc etc until it breaks....makes an unforgettable buzzing sound. Will happen at high speeds..
since we'll never get the NTSB report on this one ryanpilot could be correct...
flutter at high speed is caused by..too big a gap between the control surface and wing...weak servo, control horn, clevis, or control rod that will flex. even broken or loose hinges. Did the engine size contribute to the accident perhaps. might have over stressed some of the control surface componets on a previous manuver. Sealing the gap would have prevented flutter.
flutter also can effect our full scale cousins..but that issue is layed to rest in the testing stages.or now a days on the computer.before production begins.
Now before you get worried flutter won't have an effect on trainers. Should have seen the gap I had on my LT-40. a hignge pin widith worth...
Sorry for the loss of the plane
flutter is caused by airflow between the wing and control surfaces which causes the control surface to deflect. which causes the airflow to reverse and the control surface to deflect the other way, which causes the airflow to reverse etc etc until it breaks....makes an unforgettable buzzing sound. Will happen at high speeds..
since we'll never get the NTSB report on this one ryanpilot could be correct...
flutter at high speed is caused by..too big a gap between the control surface and wing...weak servo, control horn, clevis, or control rod that will flex. even broken or loose hinges. Did the engine size contribute to the accident perhaps. might have over stressed some of the control surface componets on a previous manuver. Sealing the gap would have prevented flutter.
flutter also can effect our full scale cousins..but that issue is layed to rest in the testing stages.or now a days on the computer.before production begins.
Now before you get worried flutter won't have an effect on trainers. Should have seen the gap I had on my LT-40. a hignge pin widith worth...
Sorry for the loss of the plane
09-21-2007 | 08:54 AM
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From: Cape TownWestern Cape, SOUTH AFRICA
RE: FLUTTER
Its amazing, this issue has been dealt with in detail by me and othe rposters in the Funtana 90! thread and others but still, out jumnp the mother Grundy's who probably have no experience with this plane or the hardware supplied. 
The Funtana 90 airframe can handle large engines without a problem. Mine flies with a Moki 135. It started life with a GMS 120 in it. It fluttered at low to medium pace in a strong headwind. I landed it with both aileron gears stripped. The fix is as the initial poster pointed out quite correctly, is to ditch the rubbish plastic control horns which belong on a 3 d fun fly and fit some 50 cc size control horns. There are three 135 powered F90s with this upgrade and teh same Hitec 635 servos, that get the cr@p flown out of them and are overspeeded on conventional wisdom, without any incidents at all. The simple answer is that H9 specced below par control horns on a plane with barn door size ailerons. So, no, the fact taht it had a Saito 180 in it was not the reason it fluttered in a down line.
The Funtana 90 airframe can handle large engines without a problem. Mine flies with a Moki 135. It started life with a GMS 120 in it. It fluttered at low to medium pace in a strong headwind. I landed it with both aileron gears stripped. The fix is as the initial poster pointed out quite correctly, is to ditch the rubbish plastic control horns which belong on a 3 d fun fly and fit some 50 cc size control horns. There are three 135 powered F90s with this upgrade and teh same Hitec 635 servos, that get the cr@p flown out of them and are overspeeded on conventional wisdom, without any incidents at all. The simple answer is that H9 specced below par control horns on a plane with barn door size ailerons. So, no, the fact taht it had a Saito 180 in it was not the reason it fluttered in a down line.
